Re: iPhone4 and iPad2 w/o 3G
I'd say teaming up your phone and iPad is just an awkward solution when a bluetooth GPS receiver is easy and pretty foolproof. Juggling two devices and keeping them charged and such seems like a pain in the neck. I am not sure that you can actually share location information between the iPhone and the iPad over a tethered connection anyhow.
Bashing about on Lake Ontario and Beyond
"Ariel" '79 Endeavour 32